Abstract

The subject of research was probability of appearance of technical roundwood timber assortments in trees according to type of felling, as well as the difference between shares of technical roundwood timber assortments according to diameter class and type of felling. The percentages of technical roundwood established in this research were compared to the planned values (assortment tables) which are applied in forestry operational bodies. Research was carried out on a sample consisting of 787 trees in thinning felling, 1025 trees in preparatory felling, 606 trees in seeding felling and 583 trees in final felling. An overall number of 3001 exemplary trees were included in the research. The age of the felling areas studied was between 59 and 91 years in the preliminary yield (thinning), 94 to 110 years in preparatory felling, 100 to 112 years in seeding felling, and 98 to 112 years in final felling areas. We think that the approach to establishing the assortment structure of even-aged beech stands taken so far is to a large extent wrong. The operative assortment tables give too high estimates of top quality timber assortments of all types of felling, except the final felling of seeding beech felling areas. Timber assortment tables that take into consideration the type of felling as one of the inputs, enable a more reliable estimate of assortment structure of the felling area and more precise planning of timber mass marked for felling. In this case, as a distinguishing factor, we took the selection criterion for marking trees for felling which is applied for the types up to, and including, the preparatory felling. For that reason, timber assortment tables were made separately for thinning and preparatory felling, and separately for seeding and final felling. On the basis of the research results, new assortment tables were made according to Croatian Standards of Forest Exploitation Products from 1995. Seeding and final felling show by ca 8–14 % higher shares of top quality timber assortment (F and L) than thinning and preparatory felling. On the other side, thinning and preparatory felling show by ca 4–15 % higher shares of technical roundwood assortment of lower quality (second-class and third-class) than seeding and final felling.

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